Gas-analysis apparatus



Jan. 15, 1929. l,698,887

' R. H. KRUEGER GAS ANALYSIS APPARATUS Filed Aug. 27. 1927 I Figi ATTORNEY Pasma Jm. 15, 1929.

UNITED STATES PATENT OFFICE.

31m I. nUEGIB, NEWABX, NEW JEISY, ASSIGNOB 'I'O CHARLES HGI'- w, m0.,01' mm, JEBSEY, A CORPORATION 0]' m m.

GAS-ANAL'YSIB APPM'I'U.

.Appunam ma mam 87, m7. sami iw. 218,881.

This improvement relates more particu- `larly to means for adjustablyvar ng the heat dissipating capacity`of therma conductivity cells,thereby' providing mechanical 5 means for equalizing the rate of heatdissiation from the cells of the gas to be anayzed and of the referencegas.

The method of gas analysis by the use of thermal conductivity cells inla Wheatstone bridge is well known, and it is known thatl for the bestresults, compensation for temperature variations should be efl'ected inorder to obtain balanced bridge conditions at different temperatures.This is especially important when the analysis cells in a Wheatstonebridge are used for measuring differentials, as is the case in ananalysis unit for determining impurities in a gas or gas mixture.

The object, therefore, of myV improvement is to provide mechanical meansor'devices for adjustably varying the heat dissipating o apacity of theindividual cells, so that by suitable adjustment an equilibrium can beobs tained in the heat dissipation, so as to eliminate errors from thissource, particularly when the apparatus is exposed to different temeratures.

O viously this compensation may be effected in various ways, but, in thepresent instance, it is preferably accomplished by providing means forinterposing, in varying amount, a shield or auxiliary heat absorbingdevice, in a manner to cut down the radiation reaching the cell walls.When the resistance thermometers are mounted in the cells it isimpossible, in ordinary commercial practice to mount the resistanceelements central, or in the same relative position in all the cells,

0 to thei'eby insure that the proper amount of heat shall be dissipated,under all test conditions, according to the calibration of theinstrument. It is also impossible to construct the resistancethermometers so that, when mounted in the cells, all the heatingelements will radiate the same amount of heat within the respectivecells.

Therefore, by means of my improvement, an such variations in the amountof heat ra iated or adapted to be dissipated through the walls'of thecells can be compensated for and, when an instrument has been onceproperly calibrated and adjusted, the readings will not requirecorrections for variations in room temperatures or for other reasons.

One formof myimprovement is shown in the accompanym drawings whereinFiguiel is a agram of thel Wheatstone bridge with my improved thermalconductivity cells;

Figure 2 shows a longitudinal section through one of the thermalconductivity cells, on the line 2- 2 of Figura 3, with mechanical meansfor adjustmg the capacity for dissipating heat; and i Figure 3 is atransverse section of a metal block or cell unit containing cells foreach of the four arms o f the Wheatstone bridge.

Referring to thedrawings and particularly to Figure 1 it'will be seenthat my improved gas analysis apparatus comprises the well knownWheatstone bridge, wherein the usual manganin ratio resistance coils R1and R2 may be inserted in adjacent arms of the bridge. l

Between the fixed resistances R1 and R2 a slide Wire S-W is shown, andmay be used for balancing the bridge. Between the slide w1 re S--WA andthe op osite point D of the bridge there is prefera ly lconnected, incircuit with a source of current such as the battery B, a milliammeterM-A, and a rheostat R for varying the flow of current.

The other arms of the Wheatstone bridge, as shown in Figure 1, containthe gas analysis cells A1 and A2, one of which is more particularlyshown in section in Figure 2.

The galvanometer G, for direct reading of the variations in the 'gasunder analysis, is placed in circuit across the points E and F -o'f thebridge.

When the ratio arms R1 and R2 are exactly alik'e in resistance andtemperature co- .eflic1ent it is quite possible that the bridge i s notin balance even when the same gas mixture is passed through bothanalysis cells A1 and A2. One reason for this is that the rate of heatdissipation in the two cells is different, due to the fact that theresistance thermometers or heating elements are not in the same relativeposition in both cells or not rafiiating the same amount of heat withinthe ce s.

Balancing the bridge by means of the slide wire S-W will not remedy thedefect if the temperature coeflicients and resistance of the two cellsA1- and A2 are different, as hereinbeforeiindicated. The pro er remedyis to vary the volume of the cham er of one or both of the analysiscells, or in some way vary or control the rate of heat dissipation so asto compensate for the difference in resistance or heat coeficicnts andobtain an equalization m the heat dissipation of the cells A1 and A2.

The cells A1 and A2 are preferably formed in a block of metal 10, which,as shown'm Figure 3, is preferably also provided w1 th holes or chambers11 and 12 for the ratio colls R1 andR, for which resistance thermometersma be substituted. In the latter case, the ce s 11 and 12 may be filledwith reference gas or they may be used in conjunction with the cells A1and A2. As will be seen in Fi re 2 the analysis thermalv conductivitycel s are provided with a resistance heatlng co1l 13 which is preferablyformed of latmum Wire Wound on a quartz rod and sea ed in a quartz tube14. The ends 15 of the heating coil are brought out through a sealincork 16 in the upper end of the tube 14, t e latter bem mounted in theupper end of the cell and hel therein by avscrew cap 17 The referencegas,

or the gas to be' analyzed, may be passed through the cell by tubes' 18and 19, the gas,

preferably entering through the tube l.

As previously pointed out, it is practlcally impossible to mount theresistance thermometers 18 and 14 absolutely central, or in the samerelative position in all the analysis or thermal conductivity cells, sothey have the same radiation and heat dissipation. Therefore, in orderto compensate for any such variations I preferably bore out the lowerend of the cell and insert therein a heavy metal plug 20, screw threadedinto the cell block 10, or at 21. The plug 20 is bored out or formedwith a pocket 22, in which a shield tube or thimble 23 is slidablymounted. The lower end of the Shield thimble is preferably closed exce tfor a screw threaded opening in which an a justing'screw 24 operates.The shank 25 of the screw 24 passes through a hole in the lower end ofthe pocket 22, in the plug 20, and is provided with a nut-like head 26,whereby the position of the shield 28 may be adjusted. In order toprevent rotation of the tubular thimble 23 a longitudinal slot 27,therein, cooperates with the end of the gas inlet tube 18, whichprojects into the cell for this purpose, as shown in Figure 2.

In operation it will be understood that, with my improvement, thereference gas or, at least, the same gas or gas mixture is first passedthrough all the analysis cells and adjustments made ofthe shields 23 toobtain equalization of the heat dissipation. When all the resistances inthe bridge are correct any out of balance is caused by unequal radiationor dissipationof heat. Heretofore, to correct for this, it required daysof tests and calibration adjustments, but with my improvement sucherrors can be eliminated in a respective resistance thermometers 13-14the few minutes, by simply adjusting theV Shield members 23 by meansof-the screws 24. The Shield thimbles 23 maybe arranged to provide forample adjustment, as indicated by dotted lines in Figure 2. The Shieldtubes 23 preferably are spaced from the lower ends of the resistancethermometers and slide u thereabout without contact therewith. hus bycovering or rmcovering the lower ends of the heat dissipation of theseveral thermal conductivity gas analysis cells can be equalized andproperly calibrated to give correct readings over a wide range of temeratures.

While I have shown the pre erredl form of my improvement, it will beunderstood that I do not wish to be limited to the specific de-f tailsof construction shown for various modifications therein may be madewithout departing from the splrit and scope of the'invention.

Having thus described my invention, what I claim as .new and desire tosecure by Letters Patent, is

1. A gas analysis apparatus comprising a resistance heating elementmound in a thermal conductivity cell having Walls adapted for dissiating heat, and adjustable means for-varymg the capacity of said wallsfor dissipating the heat.

2. A gas analysis apparatus comprising a thermal conductivity cell, thewalls of which are adapted to facilitate the dissipation of heat, aresistance heating element mounted in said cell, and mechanical meansfor modifying the rate of dissipation of the walls of the cell of heatradiated from said heating element.

3. A gas analysis apparatus comprising thermal conductivity cells forthe reference 105 gas and for the analysis gas, resistance heatingelements in each cell, and means associated with the heating elements ofthe respective cells for equalizing the heat dissipation of the cells.

4. A gas analysis apparatus comprising a plurality of thermalconductivity cells, resistance heating elements in said cells, andmechanical devices associated With said cells' for varying the capacityof the respective cells for dissipating heat.

5. A gas analysis apparatus comprising a thermal conductivity cell. withwalls adapted for absorbing and dissipating` heat, a resistance heatingelement mounted in said cell, a device for varying the discharge of heatfrom said resistance element to the walls of the cell, and means forefecting relative adjustment between said device and the resistanceelement. w

6. A gas analysis apparatus comprising a thermal conductivity cell, aresistance heating element mounted in said cell, a tubular shieldmounted for movement between said heating element and the walls of thecell to vary the heat dissipaticn of the cell and a the walls of thecell to vary the heat dissipascrew for moving said shield to vary itspotion of the cell, and means for vaiying the sition in the cell.position of the shield in the cell. 10 7. A gas analysis apparatuscomprising a This specification signed this 25th day of 5 thermalconductivity cell, a heating element August, 1927. mounted in said cell,a Shield mounted for movement between said heating element and i RICHARDH. KRUEGER.

GERTIFIGATE or coRREcTI'oN.

Patent No. 1,698, 887. Granica January 15, 1929, :o

RICHARD H. KRUEGER.

It is hereby certified that the name of the ,assignee in the abovenumbered patent was erroneously written and printed as "CharlesEngalhard, AInc.'', whereaa said-name should have been written andprinted as "Charles Engelhard, Inc.", aa shown by the records ofassignments in this office; and that the said Letters Patents should beread with this correcton thereiu that the same may conform to the recordof' the case in the Patent Office.

Signed and sealed this 26th day of February, A. D. 1929.

g M.J.` Moore. (Seal) Acting Commiaaioner of Pateuts.

DlsoLAlMa-.Ry i

1,698,887.-R'ichard H. Kr'ueger, Newark, N. J. GAs-ANALYsIs APPanA'rUs.Patent dated Januaiy 15, 1929. 'Disclaimer filed August 9, 1930, by theassignee, Charles Eagelhard, Inc. l Hereby enters this disclaimer vtoclaim 3 of said patent which is in the following words, to witz.

3. A gas analysis apparatus .comprising thermal conductivity cells fqrthe reference gas and for the analysis gas, resistance heating elementsin each cell, and means associated With the heating elements of therespective cells for equalizing the heat dissipation of the cells."[Ofilcal Gazette August 26', 1930.]

